Back in the 70s and 80s I was involved with a very fast growing business (growth rate for 20 years was 5%/month compounded). In the early years it was easy to keep people involved because we were promoting people quickly (we emphasized internal promotion). Then it got harder. The boredom after about 3 years became evident. You could not promote everyone.

One solution we settled on was to cross train people who wanted a new challenge. Put them into a different part of the business under a mentor and let them learn something new. Some made their move permanent; others went back to what they had been doing with new states to challenge their thinking.

Another was to upgrade our vacation policy: every third year, you got a month of paid vacation time.

A third, restricted to department heads and up, was to encourage them to volunteer as sessional teachers at local colleges for one day a week, usually doing seminar sessions on their specialty.

A fourth was to offer the opportunity for staff to take learning sabbaticals of up to two years (there was a contractual requirement to return for an equivalent period of time); most who took that option went back to get MSc or MBA degrees. If they graduated and stayed with us, we covered their school costs.

All the programs were designed to provide fresh challenges and the opportunity to get out of that 3-year rut without moving elsewhere. They helped us retain a lot of very capable people.